This invention is in the field of optical liquid particle analyzers. In an embodiment, this invention relates generally to systems and methods for improving data quality and protecting optical components, such as a laser, photodetector, or optical lens elements from damage caused by over-heating. In an embodiment, this invention also relates generally to methods and systems for adjusting optical source intensity and acquisition of data during periods in which bubbles are present in the particle analyzer and/or periods in which the fluid is either not flowing or flowing at an optimal rate.
A large portion of the micro-contamination industry and clean manufacturing industries is reliant on the use of optical particle counters, such as are described in a number of U.S. Patents, including U.S. Pat. Nos. 3,851,169, 4,348,111, 4,957,363, 5,085,500, 5,121,988, 5,467,188, 5,642,193, 5,864,399, 5,920,388, 5,946,092, and 7,053,783. Particle counters are also described in U.S. Pat. Nos. 4,728,190, 5,282,151, 6,859,277, and 7,030,980, which are hereby incorporated by reference in their entirety.
Optical liquid particle sensors and counters are useful in a variety of industrial applications including in semiconductor, pharmaceutical and microelectronics industries. In some industrial settings, optical liquid particle sensors and counters provide an important tool for continuously monitoring the composition and purity of liquids used in a process, for example, in the production of pharmaceutical products subject to stringent regulatory requirements relating to particulate contaminants. In other industrial settings, optical liquid particle sensors and counters provide an important tool for providing quality control analysis. It is particularly advantageous to rapidly identify when a fluid is contaminated with unwanted particles so that the process can be stopped at an early stage, thereby avoiding wasteful manufacture of defective product. For example, in semiconductor and other clean-room settings, or industries requiring sterile and pure production (e.g., pharmaceuticals), material liquids that are used to make the end products are continuously monitored to ensure adequate purity and that any unwanted particles suspended in the fluid are within an acceptable tolerance range.
An issue with modern liquid particle counters is damage to internal components of the liquid particle counter, such as the detector array or the optical source, caused by changes in flow rates or bubbles in the flow chamber of the particle counter, especially in systems that utilize a high powered optical source in order to detect smaller particles. For example, when bubbles, which may be orders of magnitude larger than the particles of interest, pass through the flow chamber they scatter a large amount of electromagnetic radiation which can overload and damage the collection and detection systems of the particle counter. Additionally, if the flow rate of the liquid through the flow chamber of the particle counter is too low or stopped, the optical source may boil the liquid which scatters intense radiation throughout the particle viewing flow chamber and into the optical system, damaging the collection and detection systems and/or overheating and damaging the optical source itself.
Bubbles and changes in flow rate through the liquid particle counter also cause data integrity issues. For example, presently available optical liquid particle counters cannot distinguish between a bubble and a solid particle as they both obscure, scatter or emit electromagnetic radiation. Therefore, as bubbles pass through the flow chamber of a liquid particle counter they are falsely counted as solid particles, artificially raising the reported contamination of the system being analyzed. Further, liquid particle counters are calibrated for a specific flow rate or a range of flow rates. Changes in the flow rate through the system, either increases or decreases, alter the way in which particles obscure, scatter or emit electromagnetic radiation as they pass through the flow chamber. Thus, a non-optimized or non-normal flow rate can cause the particle counter to mischaracterize the particles, for example, by miscounting or mischaracterizing the size of the particles.
It can be seen from the foregoing that there remains a need in the art for improved liquid particle counters which reduce or eliminate damage to internal components due to flow issues or bubbles within the flow chamber. Further, there remains a need for liquid particle counters with improved resolution and reliability which account for false positives caused by bubbles and mischaracterizations caused by changes in flow rate.